I. Field of the Invention
The present invention relates generally to dental procedures and, more particularly, to a dental procedure for preparing tooth structure for bonding with composite material.
II. Description of the Prior Art
When decay is removed from tooth structure, such as dentin and enamel, the resulting cavity caused by the removal of the tooth decay must be filled in order to protect the tooth from further decay, infection and the like. Both amalgam and composites have been used to fill the cavity preparation performed by the dentist.
When amalgam is used to fill the cavity preparation performed by the dentist, the dentist typically undercuts the enamel thus forming a pocket in the tooth having a relatively small opening exposed to the exterior of the enamel . Amalgam is then forced into the pocket and is held in place by a mechanical retention with the tooth structure. Although amalgam has proven adequate in filling cavity preparations, it is cosmetically undesirable due to its silver or dark color.
There are, however, composites and other similar materials (hereinafter collectively referred to as composites or composite materials) which are of the same color as the tooth and are used to fill the cavity preparation performed by the dentist when removing the tooth decay. Since these composites are of the same color as the tooth, they are cosmetically more desirable than amalgam.
In order to prepare the tooth structure, i.e. the enamel and dentin and associated tooth material, an acid is typically used to etch the enamel to enhance the bond between the composite and the enamel. The dentin, however, should not be etched because of problems with pulpal insult from acid which can result in increased pulpal sensitivity and other complications.
Consequently, in order to protect the dentin from the acid etch, the dentin is first covered with a primer which not only protects the dentin from the acid during a subsequent enamel etch, but also removes the smear layer caused by the traditional rotary drill used by dentists.
After the dentin has been coated with the primer, an acid etch is then used to etch the enamel surrounding the opening in the tooth structure. FIG. 1 depicts such an acid etch at approximately 3500 magnification. As can be seen from FIG. 1, the acid etch in the enamel caused large crevices and peaks in the enamel.
After the acid etch, the acid is rinsed away with water and the tooth is dried. After drying, a bonding agent is applied to both the dentin as well as the etched enamel. The composite is then applied to the dentin and etched enamel on top of the bonding agent, cured with a light whereupon the composite restoration is completed.
There are, however, a number of disadvantages with this previously known process for cavity preparation for composites. One disadvantage is that the entire procedure for cavity preparation using a composite is a time consuming and relatively difficult procedure for the dentist.
A still further disadvantage of the previously known procedure is that it is very difficult, if not altogether impossible, for the dentist to apply the primer only to the dentin while leaving the enamel surrounding the cavity preparation exposed for the subsequent acid etch. This is particularly true since the dentin-enamel junction forms only a fine line oftentimes difficult for the dentist to see. Consequently, as a practical matter, the bonding is applied by the dentist not only to the dentin but also to portions of the enamel . Any primer applied to the enamel, however, will prevent the desired acid etch of the enamel and thus degrade the overall integrity of the bonding between the enamel and the composite.
A still further disadvantage of the previously known cavity preparation for composites is that the acid etch creates relatively deep crevices and high peaks in the area of the enamel which is etched as shown in FIG. 1.
While the deep crevices and high peaks of the enamel caused by the acid etch enhance the overall bond between the composite and the enamel, moisture from the rinse following the acid etch can become entrapped in the crevices. Any remaining moisture entrapped within the crevices of the acid etch from insufficient drying weakens the bond between the composite and the enamel.
A still further disadvantage of these previously known cavity preparations for composites is that the polymerization process of the composite places varying magnitudes of stress upon the bond between the dentin and the composite. Such stresses can result in increased sensitivity between the composite and the dentin, especially where gaps exist between the composite and the dentin. Such gaps can result in small movement of the composite when the patient chews or otherwise applies pressure to the composite which also results in increased sensitivity for the tooth.
A still further disadvantage of the previously known cavity preparation using acid etch on the enamel is that gaps frequency result between the composite and the enamel due to the large peaks and valleys in the enamel from the acid etch. These gaps increase the risk of microleakage which allows contaminants to infiltrate the gaps in the enamel and cause additional decay of the tooth from the microleakage.